Development of Brittle Crack Arrest Toughness K_<ca> Test Method : Brittle Crack Arrest Design for Large Container Ships-2

概要

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Brittle fractures of the hull structure cause serious structural, fatal and environmental damage once they happen. Therefore, ships are basically designed and constructed in such a way to prevent brittle cracks from occurring. Further, if by chance a brittle crack occurs, it is essentially and extremely important that a backup brittle crack arresting function is provided to arrest its propagation and to ensure structural reliability. As an evaluation method of arrest toughness, several test methods have been developed: Robertson test (1953), ESSO test (1955), Double tension test (1958) and others. At the moment temperature, the gradient type ESSO test is the most popular method for the determination of the arrest toughness of material used because of its convenience. However, there is no code or standard ESSO test despite its long history. In this report, with the goal of developing a standard of ESSO test, effects of testing conditions-that is, thickness of tab plate, width of tab plate, distance between pins, temperature gradient and crack length-on the evaluated K_<ca> values are investigated. Investigation is based on many large scale crack arrest tests with 16,50 and 80mm thick low carbon steel plates conducted by four research groups in Japan. This research has been conducted by the research committee of the Nippon Kaiji Kyokai (ClassNK) and its results have been summarized and incorporated in their "Guidelines on Brittle Crack Arrest Design".